The present invention relates to a bolt protected from loosening itself on one hand, and also to a method of protecting a bolt from loosening itself on the other hand.
Some proposals have been made to prevent a bolt set in place from being loosened unintentionally. In one of the well known proposals, a cutout is formed in the threaded shank of a bolt and along periphery thereof so as to secure in the cutout an appropriate spring or a resilient plastics piece.
However, such a proposal would raise manufacture cost due to the secondary machining of the threaded shank and a considerably intricate work to set the spring or resilient piece in place. Further, these spring and piece would undesirably cause an additional torque to be required even to initially fasten such a bolt into a female-threaded hole, thereby rendering uneasy the bolt fastening operations. In addition, deterioration of the spring or elastic piece would take place along the course of time, impairing their effect of locking the bolt.
Primary objects of the present invention, that was made in view of these problems in the prior proposals, are to provide a surely lockable bolt and a method of surely locking a bolt in place wherein the bolt""s head is simply improved as to its seat surface without need of any additional member.
In order to achieve the objects, here is employed the following technical means. Namely, a self-lockable bolt xe2x80x98Axe2x80x99 provided herein does comprises a threaded shank 1 continuing to an enlarged head 2 that has a seat surface 3 gently inclined sideways in one direction. The angle xcex1 of the inclined seat surface 3 is selected herein within such a range that an upper side of an article xe2x80x98Cxe2x80x99 to be tightened with the bolt xe2x80x98Axe2x80x99 will be pressed in a normal direction with its head 2 and simultaneously a stress is imparted to the bolt in such a transverse direction as tending to shear the bolt""s shank, when a predetermined torque is applied to the bolt so as to fasten same into a female-threaded hole xe2x80x98Bxe2x80x99.
The method proposed herein for preventing a bolt from loosening itself does characteristically comprise the steps of preparing a self-lockable bolt xe2x80x98Axe2x80x99 having a threaded shank 1 continuing to an enlarged head 2 that has a seat surface 3 gently inclined sideways in one direction and at an angle xcex1, and then fastening the bolt with a predetermined maximum torque into a female-threaded hole xe2x80x98Bxe2x80x99 to such an extent that due to the angle xcex1 an upper side of an article xe2x80x98Cxe2x80x99 to be tightened with the bolt xe2x80x98Axe2x80x99 will be pressed in a normal direction with the head 2 and simultaneously a stress will be imparted to the bolt in such a transverse direction as tending to shear the shank 1.